Acid cadmium plating



N Drawing. Application September 13, 1957 Serial No. 683,691

12 Claims. (Cl. 204-50) The present invention relates generally to the electroplating art and is more particularly concerned with novel compositions for use in aqueous acid cadmium fiuoborate electroplating baths, with novel baths of this type having unique and valuable properties and with a new process for electrodepositing cadmium involving the use of said compositions and baths and affording special new advantages and results.

Cadmium, plated from the usual acid fluoborate bath compositions, is dull and frosty in appearance, and exhibits poor throwing power of the bath, in that recessed areas of an irregularly shaped surface are not uniformly covered by the cadmium deposit. The principal functional difference between acid cadmium fluoborate baths and the more conventional cadmium cyanide plating formulations, is that the former have very poor throwing or covering power, while the latter are excellent in both of these properties. My invention provides an additive to cadmium fluoborate cadmium plating baths that permit them to compete commercially with cadmium cyanide baths With respect to throwing and covering powers, while retaining the well recognized non-embrittling properties of the fiuoborate baths. Cadmium cyanide baths are notorious for their embrittling effect, especially on hardened steel, or more commonly on spring steel. Thus, my invention provides a cadmium fluoborate plating bath that is practically as good as the cyanide bath with respect to covering power, but without embrittling effects on hard steel, thus providing a means for effectively cadmium plating hard steel uniformly without at the same time causing embrittlement. This is of principal importance in the manufacture of modern aircraft structures, since they can best be protected from corrosion by cadmium plating, but must not be embrittled thereby, for obvious reasons.

These results are obtainable for the first time as a result of my surprising discovery upon which this invention in all its various aspects is predicated. This discovery, succinctly stated, is that certain non-ionic surfactants in certain concentrations in cadmium fluoborate plating baths possess characteristics hitherto unknown to either these surfactants or to the baths containing them. Thus both the nature of the surfactant and the amount or concentration of the surfactant in the bath are critical, but I have found that there is certain latitude as to both these factors. In fact surfactants which have been used in electroplating to lower surface tension can be used to obtain the results of this invention, but such use requires such high concentrations of these surfactants that the surfactants are more in the nature of bath constituents.

In general the surfactants contemplated by this invention are commonly known as non-ionic and are selected from the general class of polyethylene oxide condensation products, the hydrophobic portions of which are selected from the group comprising phenols, alcohols, acids, and amines.

Compounds of this general type are widely used in the textile industry and are discussed ina paper by J elinek v 2,93,934 Patented July 7, 1959 ice et al. in the Textile Research Journal, vol. XXIV, No. 8 (August 1954), and in an article by the same authors in Industrial and Engineering Chemistry, vol. 46, pp. 1930-4934 (September 1954). Therefore, no claim is laid to these materials, as such, but only to their use as additives or bath constituents in cadmium fluoborate plating bath formulations, and their presence in specially formulated compositions of matter designed for use as additives to cadmium fiuoborate plating baths, in order to insure the production of cadmium deposits therefrom that meet the requirements of both uniform corrosion protection and non-embrittlement of the basis metal, usually hardened steel.

Broadly speaking, the additives of my invention may be represented by the general formula:

wherein R represents a typical hydrophobic or relatively water insoluble group, usually derived from a fatty acid, a fatty alcohol, an alkyl phenol, an aryl phenol, a rosin acid, or an amine, or similar hydrophobic type of compound, and n represents a numerical value from about 5 to about 50, usually from around 9 to around 30. Their methods of preparation are therefore matters of record. They are marketed commercially under a wide variety of trade-names such as, for example, Tweens, Emulphors, Nonisols, lgepals, Tritons, Polyrads, Pluronics, Tergitols, and Priminox among others.

The corresponding propylene oxide condensation products can be made, and while some of them are on the market, they are in general less water soluble than the corresponding and more common ethylene oxide condensation products and therefore less desirable, in general, as addition agents in plating baths although some may be effective if their bath solubility is sufiicient to produce the desired effects.

The additives of my invention greatly increase the throwing and covering powers of cadmium fluoborate plating baths, which means that cadmium deposits therefrom more uniformly on the low and high current density areas of an irregularly shaped cathode, thus affording better protection against corrosion to the low current density areas without building up deposits of excessive and unnecessary thickness on the high current density areas. These beneficient properties are possessed to a high degree by the additives of my invention, so that they permit cadmium fluoborate plating baths to approximate the older cadmium cyanide baths in these properties, which in itself is unique.

The additives of this invention are applicable to any commercially operable cadmium fiuoborate plating bath. Such plating baths usually consist of an aqueous solution of cadmium fluoborate at a concentration of around 20 to 40 ounces per gallon (150-300 grams per liter) and usually contain ammonium fluoborate in concentrations of from about 8 to 16 ounces per gallon (60 to grams per liter). These baths are usually operated at room temperature within the pH range of about 1 to about 4. Operated without addition agents, such baths produce dark, coarse, lusterless deposits and have very poor throwing and covering powers. The additives of this invention are designed to be added to such baths in amounts sufficient to produce the results desired with respect to lighter colored or semi-bright deposits, refined grain structure, homogeneity of deposit and uniformity of surface coverage. The amount of such additives required will depend on the additive composition, but will usually be found to be from about 8 to about 50 grams per liter, or from about 1 to about 6 ounces of additive per gallon of plating bath. Usually around 15 to 20 grams per liter or around 2 to 2.5 ounces of additive per gallon of plating bath will be found to give the desired results.

The following is a specific, but not limiting, example of a commerically operable cadmium fluoborate plating bath embodying this invention:

Example I Grams per liter Cadmium fluoborate 250 Ammonium fluoborate 90 Surfactant A-l 15 In this formula Surfactant A-l designates a product available on the market under the trade-name Igepal CO- 710 of the Antara Chemicals Division of General Aniline and FilmCorporation. In chemical terms this product is polyoxyethylanated nonylphenol containing approximately 11 mols of ethylene oxide condensed with approximately one mol of nonylphenol.

Other surfactants of this A series which may be substituted in whole or in part for Igepal CO-7l0 in the bath of Example I, include the following:

(1) A'2, Igepal CO-630, aproduct in which the ratio of polyethylene oxide to nonylphenol is lower, i.e. nine to ten mols per mol of nonylphenol;

(2) A3, 'Igepal CO-730, a similar compound in which the mol ratio is about fifteen to one of nonylphenol;

(3) A-4, Igepal CO-850, as above but with a mol ratio of about twenty to one of nonylphenol;

(4) A-5, Igepal CO-880, another wherein the imol ratio of polyethylenoxide to nonylphenol of about thirty to one;

(5) A 6, Tergitol Nonionics, NPX, NP 35, or NP 40 (Carbon and Carbide Chemicals Co.) which are alkyl phenyl ethers of polyethylene glycol of various ratios;

(6) A-7, Priminox 21 and 32 (Rohm and Haas) are aliphatic tertiary alkyl amines condensed with polyethylene oxide in trial ratios of 15 and 25 to one, respectively;

(7) A-8, Triton X100 (Rohm-and Haas) which is a condensation product of polyethylene oxide with an alkyl aryl alcohol;

(8) A-9, Nonisols (Alrose Chemical Co.) which are fatty acid esters of polyethylene oxide; and,

(9) A-10, Kyro E. O. (Procter and Gamble), an alkyl phenol-ethylene oxide condensate.

Other illustrative examples of commercially operable plating baths of this invention containing a surfactant of an alternative type are:

Example ll Grams per liter Cadmium fluoborate 250 Surfactant B-2 15 The E series of surfactants for purposes of this disclosure are essentially certain condensation products of ethylene oxide with amines. The compositions of this group which are especially effective for the purposes of this invention contain significant amounts of unreacted amine. Products of this description are offered on the market at the present time by Hercules Powder Co. under the general trade-name Polyrad and they are described by the manufacturers to be condensation products of ethylene oxide with a rosin amine, in particular dehydro- "abietylamine (technical grade).

Surfactant B-l is Polyrad 1100 which is a completed reaction product of the above rosin amine with ethylene oxide in the molecular ratio, of one to 11, respectively.

Surfactant 13-2 is Polyrad' 1110, a composition containing the B-1 reaction product and about 10% free,

will be generally the same with all bath formulations. Thus under Examples I, II, and III the temperature of the plating bath will be maintained in the range of about 60 F. to 100 F. and preferably between 70 F. and F. the pH may range from about 1 to 3 with my preference being from 2 to 2.5. Cathode current density may range from about 10 to 50 amperes per square foot but preferably will be between 20 and 30 amperes per square foot.

In actual operations I have obtained best results through the use of the following bath composition:

Example IV Grams per liter Cadmium fluoborate 250 Ammonium fluoborate Surfactant B-2 15 ,7 Hardened steel work pieces plated in baths of Example IV under the operating conditions stated above have been completely covered with a cadmium deposit of uniform appearance, fine-grained structure, and with coverage of the basis metal approximating that obtained from a cadcyanide plating bath, but without any of the objectionable effects, such as embrittlement, usually encountered in cyanide bath plating. The throwing and covering powers-of the bath of Example IV are far superior to those of any cadmium fluoborate plating bath heretofore known in the art, and in addition no deleterious effects such as embrittlement of hardened or spring steel have been encountered.

Since commercial operators of cadmium fluoborate plating baths make up their solutions from cadmium fluo- This liquid addition agent is designed to be added to a cadmium fluoborate plating bath in the proportion of about 30 cubic centimeters of brightener per liter of plating bath or about 4 ounces'of brightener per gallon of plating bath. Cadmium fluoborate concentrate can be added to the above mixture, if so desired, to render it specific for use in cadimum fluoborate plating baths.

Other additives disclosed in the foregoing specifications "can also be mixed with water a-nd/ or cadmium fluoborate "solutions in proper proportions to make additive products "for cadmium fluoborate plating baths as hereinbefore disclosed. D

Having thus described this invention in such full, 'clear, concise and exact terms as to enable any person skilled in the art to which it pertains to make and use the same, and having set forth the best mode contemplated of carrying out this invention, I state that the subject matter which I regard as being my invention is particularly pointed out and distinctly claimed in what is claimed, it being understood that equivalents or modifications of, or substitutions for, parts of the above specifically described embodiments of the invention may "be made without departing from the scope of the invention as set forth in what is claimed.

What is claimed is:

1. An aqueous cadmium fluoborate electroplating bath containing in sufficient amount to provide a uniform and bright cadmium deposit a bath-soluble, non-ionic surfactant which is a polyethylene oxide condensation prodnet, the hydrophobic portion of which is selected from the group consisting of alkyl phenols, aryl phenols, fatty alcohols, fatty acids and rosin amines.

2. An aqueous cadmium fiuoborate electroplating bath containing between about one and about six ounces per gallon of a bath-soluble, non-ionic surfactant which is a polyethylene oxide condensation product, the hydrophobic portion of which is selected from the group consisting of alkyl phenols, aryl phenols, fatty acids, fatty alcohols, and rosin amines.

3. An aqueous cadmium fiuoborate electroplating bath containing in suificient amount to provide a uniform and bright cadmium deposit a bath-soluble, non-ionic surfactant prepared by reacting polyethylene oxide with a rosin amine in the molecular ratio respectively of about eleven to one.

4. An aqueous cadmium fluoborate electroplating bath containing between about one and about six ounces per gallon of a bath-soluble, non-ionic surfactant prepared by reacting polyethylene oxide with a rosin amine in the molecular ratio, respectively, of about eleven to one, and also containing about excess of free unreacted amine.

5. In the process for electrodepositing cadmium, the step comprising depositing cadmium from an aqueous cadmium fluoborate bath containing in solution a bathsoluble, non-ionic surfactant which is a polyethylene oxide condensation product, the hydrophobic portion of which is selected from the group consisting of alkyl phenols, aryl phenols, fatty acids, fatty alcohols, and rosin amines, said surfactant being present in amount sufiicient to provide a bright and uniform cadmium deposit.

6. In the process for electrodepositing cadmium, the step comprising depositing cadmium from an aqueous cadmium fiuoborate bath containing in solution between about one and about six ounces per gallon of a bathsoluble, non-ionic surfactant which is a polyethylene oxide condensation product, the hydrophobic portion of which is selected from the group consisting of alkyl phenols, aryl phenols, fatty acids, fatty alcohols, and rosin amines.

7. In the process for electrodepositing cadmium, the step comprising depositing cadmium from an aqueous cadmium fiuoborate bath containing in solution a bathsoluble, non-ionic surfactant, said surfactant being present in amount sufiicient to provide a bright and uniform cadmium deposit and having been prepared by reacting polyethylene oxide with a rosin amine in the molecular ratio, respectively, of about eleven to one.

8. In the process for electrodepositing cadmium, the

step comprising depositing cadmium from an aqueous cadmium fluoborate bath containing in solution between about one and about six ounces per gallon of a bathsoluble, non-ionic surfactant prepared by reacting polyethyleneoxide with a rosin amine in the molecular ratio, respectively, of about eleven to one, and also containing about 10% excess of free unreacted amine.

9. An aqueous cadmium fluoborate electroplating bath containing in sufficient amount to provide a uniform and bright cadmium deposit a bath-soluble, non-ionic surfactant having the formula: R(CH .CH O)n-H, in which n is a number between five and fifty and R represents a hydrophobic group selected from the group of hydrophobic organic compounds consisting of fatty acids, fatty alcohols, alkyl phenols, aryl phenols, and rosin amines.

10. A composition of matter efiected in amounts of from 8 to 59 grams per liter of aqueous cadmium fluoborate electroplating baths to provide uniform and bright cadmium deposits, said composition containing cadmium fiuoborate and a bath-soluble, non-ionic surfactant in the form of a polyethylene oxide condensation product having a hydrophobic portion selected from the group consisting of alkyl phenols, aryl phenols, fatty alcohols, fatty acids and rosin amines.

11. A. composition of matter having special utility as an additive for a cadmium fluoborate plating bath and being effective in amounts of from 8 to grams per liter of said bath to provide uniform and bright cadmium deposits, said composition containing cadmium fluoborate and a bath-soluble non-ionic surfactant made by reacting polyethylene oxide with a rosin amine in the molecular ratio of about eleven to one, and also con taining about 10 percent excess of unreacted amine.

12. A composition of matter having special utility as an additive for a cadmium fluoborate electroplating bath and being effective in amounts of from 8 to 50 grams per liter of said bath to provide uniform and bright cadmium deposits, said composition containing cadmium fluoborate and a bath-soluble, non-ionic surfactant made by reacting polyethylene oxide with dehydroabietylamine in the molecular ratio of about eleven to one, and also containing about 10 percent excess of unreacted amine.

2,547,152 Hoffman Dec. 28, 1948 

1. AN AQUEOUS CASMIUM FLUOBORATE ELECTROPLATING BATH CONTAINING IN SUFFICIENT AMOUNT TO PROVIDE A UNIFORM AND BRIGHT CADMIUM DEPOSIT A BATH-SOLUBLE, NON-IONIC SURFACTANT WHICH IS A POLYETHYLENE OXIDE CONDENSATION PRODUCT, THE HYDROPHOBIC PORTIONS OF WHICH IS SELECTED FROM THE GROUP CONSISTING OF ALKYL PHENOLS, ARYL PHENOLS, FATTY ALCOHOLS, FATTY ACIDS AND ROSIN AMINES. 